Research progress and potential of new enhanced oil recovery methods in oilfield development

This paper reviews the basic research means for oilfield development and also the researches and tests of enhanced oil recovery(EOR)methods for mature oilfields and continental shale oil development,analyzes the problems of EOR methods,and proposes the relevant research prospects.The basic research means for oilfield development include in-situ acquisition of formation rock/fluid samples and non-destructive testing.The EOR methods for conventional and shale oil development are classified as improved water flooding(e.g.nano-water flooding),chemical flooding(e.g.low-concentration middle-phase micro-emulsion flooding),gas flooding(e.g.micro/nano bubble flooding),thermal recovery(e.g.air injection thermal-aided miscible flooding),and multi-cluster uniform fracturing/water-free fracturing,which are discussed in this paper for their mechanisms,approaches,and key technique researches and field tests.These methods have been studied with remarkable progress,and some achieved ideal results in field tests.Nonetheless,some problems still exist,such as inadequate research on mechanisms,imperfect matching technologies,and incomplete industrial chains.It is proposed to further strengthen the basic researches and expand the field tests,thereby driving the formation,promotion and application of new technologies.

Effect of CO_(2)flooding in an oil reservoir with strong bottom-water drive in the Tahe Oilfield,Tarim Basin,Northwest China

The dissolution and diffusion of CO_(2)in oil and water and its displacement mechanism were investigated by laboratory experiment and numerical simulation for Block 9 in the Tahe oilfield,a sandstone oil reservoir with strong bottom-water drive in Tarim Basin,Northwest China.Such parameters were analyzed as solubility ratio of CO_(2)in oil,gas and water,interfacial tension,in-situ oil viscosity distribution,remaining oil saturation distribution,and oil compositions.The results show that CO_(2)flooding could control water coning and increase oil production.In the early stage of the injection process,CO_(2)expanded vertically due to gravity differentiation,and extended laterally under the action of strong bottom water in the intermediate and late stages.The CO_(2)got enriched and extended at the oil-water interface,forming a high interfacial tension zone,which inhibited the coning of bottom water to some extent.A miscible region with low interfacial tension formed at the gas injection front,which reduced the in-situ oil viscosity by about 50%.The numerical simulation results show that enhanced oil recovery(EOR)is estimated at 5.72%and the oil exchange ratio of CO_(2)is 0.17 t/t.

Quantitative characterization of deep fault-karst carbonate reservoirs: A case study of the Yuejin block in the Tahe oilfield

The Ordovician reservoirs in the Tahe oilfield are dominated by fractured-vuggy carbonate reservoirs, of which fault-karst reservoirs are a hot topic in recent years. Fault-karst reservoirs feature high production, large burial depth, and strong heterogeneity under the control of faulting and karstification. Based on geological, logging, and seismic data, this study classified the Ordovician fault-karst reservoirs in the Yuejin block of the Tahe oilfield into three types, namely karst-cave, dissolved-vug, and fractured types, and established the integrated identification criteria of the three types of reservoirs. This study characterized karst caves, dissolved vugs, and multi-scale faults through seismic wave impedance inversion and frequency-domain detection of multi-scale faults. 3D geological models of different types of reservoirs were built using the combined deterministic and stochastic methods and characterized the spatial distribution of multi-scale faults, karst caves, dissolved vugs, and physical property parameters of reservoir. This study established the method for the geological modeling of fault-karst reservoirs, achieved the quantitative characterization and revealed the heterogeneity of fault-karst reservoirs. The karst-cave and dissolved-vug types are high in porosity and act as reservoirs, while the fractured type is high in permeability and act as flow pathway. This study lays the foundation for the development index prediction, well emplacement, and efficient development of the fault-karst carbonate reservoirs.

Production evolution patterns and development stage division of waterflooding oilfields

The continuous growth of recoverable reserves in a waterflooding oilfield has a significant impact on the patterns of production evolution. A new production evolution model is established by improving the Weng Cycle model. With the new model, the statistical correspondence between the production decline stage and the reserve-production imbalance is clarified,and the correlation of water cut with the recovery percent of recoverable reserves is discussed, providing quantitative basis of reservoir engineering for dividing development stages of oilfield and defining mature oilfields. According to the statistics of oilfields in eastern China, the time point corresponding to the reserve-production balance coefficient dropping to less than 1dramatically is well correlated the beginning point of production decline, thus the time when the reserve-production balance coefficient drops dramatically can be taken as the initiation point of production decline stage. The research results show that the water cut and the recovery percent of recoverable reserves have a good statistical match in the high water cut stage, and it is more rational to take both the start point of production decline stage and the water cut of 90%(or the recovery percent of recoverable reserves of 80%) as the critical criteria for defining a mature oilfield. Five production evolution patterns can be summarized as follows: growth–peak plateau–stepped decline, growth–stepped stabilizing–stepped decline, growth–stepped stabilizing–rapid decline, growth–peak plateau–rapid decline, and growth–continuous decline.

Development technologies for Triassic Chang 7 shale oil in Ordos Basin: A case study of Qingcheng Oilfield, NW China

The reservoirs in the seventh member of the Triassic Yanchang Formation (Chang 7 Member) in the Qingcheng Oilfield of the Ordos Basin are characterized by thin sandbody, tight rocks, high heterogeneity, low formation pressure coefficient, and complex geomorphology. Through the efforts in the stages of exploration, appraisal, pilot testing and development, a series of key technologies have been formed, including “sweet spot” optimization, differentiated three-dimensional well deployment, fast drilling and completion of large-cluster horizontal well, intensively-staged volume fracturing in long horizontal well, and optimization of rational production system. Furthermore, a production organization mode represented by factory-like operations on loess platform has been implemented. Application of these technologies has enabled to significantly improve the single-well production of the Qingcheng Oilfield, reduce the investment cost, and realize a large-scale and beneficial development at a full cost below $55 per barrel. In 2022, the annual production of Chang 7 shale oil in the Ordos Basin reached 221×10^(4) t, accounting for 70% of the annual shale oil production of China. The practice of development technologies in the Qingcheng Oilfield provides valuable references for efficient development of continental shale oil.

Origin of gas condensate reservoir in Fuman Oilfield, Tarim Basin, NW China

To understand the reservoir property and hydrocarbon accumulation conditions of the Middle and Upper Ordovician intraplatform shoal between ultra-deep main strike-slip faults in Fuman Oilfield of the Tarim Basin, China, the main strike-slip faults in and around well FD1 in the basin were analyzed in terms of sedimentary facies, sequence stratigraphy, intraplatform shoal reservoir property, and oil and gas origins, based on drilling data. The Yingshan Formation intraplatform shoal between the main strike-slip faults is superimposed with low-order faults to form a new type of hydrocarbon play. Firstly, hydrocarbons generated from the Lower Cambrian Yuertusi Formation source rocks vertically migrated into the second member of Yingshan Formation through the main strike-slip faults, and then migrated laterally until they were accumulated. A small amount of oil from Well FD1 came from the Yuertusi Formation source rocks in the mature stage, and a large amount of gas originated from oil cracking in the ultra-deep reservoirs. Therefore, the secondary gas condensate reservoir in Well FD1 is characterized by high gas to oil ratio, dry gas (dryness coefficient being 0.970) and hybrid origin. This new type of hydrocarbon play characterized by intraplatform shoal and low-order fault suggests a prospect of continuous hydrocarbon-bearing area in Fuman Oilfield, which will expand the ultrap-deep oil and gas exploration in the oilfield.

Evaluation of reservoir environment by chemical properties of reservoir water‒A case study of Chang 6 reservoir in Ansai oilfield,Ordos Basin,China

The Ordos Basin is the largest continental multi-energy mineral basin in China,which is rich in coal,oil and gas,and uranium resources.The exploitation of mineral resources is closely related to reservoir water.The chemical properties of reservoir water are very important for reservoir evaluation and are significant indicators of the sealing of reservoir oil and gas resources.Therefore,the caprock of the Chang 6 reservoir in the Yanchang Formation was evaluated.The authors tested and analyzed the chemical characteristics of water samples selected from 30 wells in the Chang 6 reservoir of Ansai Oilfield in the Ordos Basin.The results show that the Chang 6 reservoir water in Ansai Oilfield is dominated by calcium-chloride water type with a sodium chloride coefficient of generally less than 0.5.The chloride magnesium coefficients are between 33.7 and 925.5,most of which are greater than 200.The desulfurization coefficients range from 0.21 to 13.4,with an average of 2.227.The carbonate balance coefficients are mainly concentrated below 0.01,with an average of 0.008.The calcium and magnesium coefficients are between 0.08 and 0.003,with an average of 0.01.Combined with the characteristics of the four-corner layout of the reservoir water,the above results show that the graphics are basically consistent.The study indicates that the Chang 6 reservoir in Ansai Oilfield in the Ordos Basin is a favorable block for oil and gas storage with good sealing properties,great preservation conditions of oil and gas,and high pore connectivity.

塔里木油田超深层钻井技术进展及难题探讨

当前,塔里木油田以超深特深层为代表的深地油气资源开发对满足我国经济发展需求和保障能源安全至关重要。经过数十年的探索和实践,塔里木油田创新形成了超深复杂井井身结构设计、超深难钻地层钻井提速、超深大斜度井水平井钻井、超深复杂地层钻完井液、超深复杂地层固井、高温高压井完整性、超深复杂井井控等一系列超深层钻井技术,保障深地油气勘探获得重大突破并创造多项纪录。伴随超深井数量持续增加,工程地质条件更加复杂,井下环境更加苛刻,超深层钻井过程势必面临新的工程难题和挑战,严重制约深地油气资源安全高效开发。为此,通过概括塔里木油田钻井工程技术发展历程,系统梳理了深地钻井工程技术取得的主要技术进展,并结合新的勘探开发形势与油气开发要求,指出了塔里木油田钻井工程技术从超深层迈入特深层新时期的焦点问题及攻关发展方向,为国内外深地复杂油气井安全高效钻进提供借鉴和参考。

油田管道防垢的超疏水涂层的制备和性能研究

为解决管道结垢带来严重的经济损失和安全隐患,将超疏水涂层喷涂在管道内壁表面形成一层保护膜,以阻止流体与管壁的直接接触,研究以环氧树脂为基体,通过添加二氧化硅和氧化铝来构建表面微纳米结构,设计制备了EP-SiO_(2)/Al_(2)O_(3)超疏水涂层,通过调控2种无极纳米粒子的添加量优化涂层配方,并考察EP-SiO_(2)/Al_(2)O_(3)复合涂层的疏水和防垢性能。结果表明,当各投入5.1%SiO_(2)和5.1%Al_(2)O_(3)时涂层附着力为1级,同时接触角可达154.6°,复合涂层的垢结量明显降低,仅为同等状态下环氧涂层的16.5%。为减少油田管道的结垢和腐蚀,提高油田的经济效益和安全效益提供可行途径。

稠油化学复合冷采技术研究与应用

我国稠油储量可观,其中60%的是深层稠油,而主流的蒸汽吞吐等热采技术采收率不足20%;稠油资源开发潜力极大,积极探索新的开采方式以提高采收率是石油领域高质量发展的必然选择。本文着重阐述稠油化学复合冷采技术体系构建及其现场应用,为中深层稠油的新型绿色低成本接替技术发展提供有效方案。在分析稠油组分的基础上,细致剖析稠油结构致黏机理,包括化学降黏机理、降低启动压力梯度机理、提高驱油效果机理在内的提高采收率机理,以丰富理论认识。面向工程应用亟需,从水溶性降黏剂分子设计与合成、自组装调堵剂研发两方面出发,突破稠油绿色化学驱油体系。基于发展的稠油化学复合冷采技术,完成了3个稠油油田示范工程应用,在提高产油量、控制含水率方面取得了良好成效。进一步梳理了分子采油理论与技术、渗流理论与数值模拟技术等方面的后续发展要点,以为深层稠油的绿色高效开发接替技术研究、稠油化学复合冷采技术推广应用研究等提供启发和参考。

高含水老油田化学驱综合治理新方法及工程实践路径

针对胜利高含水老油田化学驱在科学、技术、管理、工程四个角度面临的开发矛盾,以渤76块为典型单元,在工程实践中进行具体对策分析,构建了“适、专、快、集”的老油田化学驱综合治理新方法。“适”指在老油田科学开发方式转化上,构建不同油藏类型老油田化学驱最佳介入时机模型,提出了在含水率相对较低的阶段,是适合化学驱的有利时机,高效开发方式需“适”介入。“专”指在老油田开发技术应用上,改变传统聚合物先溶解后注入的开发思路,研制可控相转化聚合物,使聚合物先注入后溶解,解决炮眼剪切降解的难题,提高油水流度控制能力,老油田开发矛盾需“专”治理。“快”指在老油田综合管理模式上,改变传统方式,即矿场提问题、研究院设计方案、化工厂生产驱油剂的“串联”管理模式,提出充分发挥矿场、研究院、生产厂三方优势的“并联”管理模式,形成针对单一油藏的产品工业化工艺包以及产业化落地方案,老油田开发技术实现“快”转化。“集”指在老油田工程应用实践上,打破老油田化学驱地面大规模建站的工程工艺模式,采用集约化撬装配注设备,实现老油田化学驱的集约快速配注,老油田工程工艺实现“集”应用。运用上述方法,在胜利油田渤76块综合含水率上升初期,实施由水驱转为可控相转化聚合物驱,实施后一年即见到明显的降水增油效果,单井日产油水平增加8.6t/d,综合含水率降低3.1%,验证了综合治理模式的可行性,为高含水老油田化学驱高效开发提供了有效路径。

滨里海盆地东缘北特鲁瓦油田石炭系层序地层与沉积演化特征

根据三维地震、测井及钻井取心等资料,结合Vail的层序划分方案,在滨里海盆地东缘北特鲁瓦油田石炭系碳酸盐岩台地内识别出7个地震层序界面及7个钻井层序界面,并将KT-Ⅰ油层组划分为3个半三级层序,KT-Ⅱ油层组划分为3个三级层序。纵向上层序格架内沉积环境由开阔台地、局限台地至蒸发台地演化。根据研究区层序格架内的古地貌恢复及沉积演化研究,将研究区古地貌—沉积演化划分为3个阶段:台地初始隆坳分异期(SQ2-SQ3层序)、差异抬升与沉积分异定型期(SQ4层序)及继承发育期(SQ5-SQ7层序)。进一步分析认为,层序格架控制下的隆坳格局分异控制了白云岩亚类在平面上的分布,低部位以泥晶云岩—膏盐岩组合和泥晶云岩—泥晶灰岩组合为主,主要为潟湖相沉积;而高部位则以泥粉晶云岩、细粉晶云岩和残余颗粒泥晶云岩为主,发育云坪相及云化颗粒滩相沉积。结果表明,区内KT-Ⅰ油层组沉积期并非前人认为的西高东低剥蚀后沉降充填,而是继承性差异沉降的结果,古地理格局总体具有“东台西槽、北高南低”特征,其始终控制着有利相带和优质储集层的发育展布。这一认识对滨里海地区油气勘探开发战略选区具有重要的指导作用。

庆城页岩油泵入式光纤监测技术实践

庆城油田页岩油水平井主体采用分段多簇细分切割体积压裂技术,但目前仍存在多簇起裂效率不清晰的问题。为了评价多簇起裂有效性及裂缝延伸规律,开展了水平井泵入式光纤测试技术先导性试验,该技术具有工艺灵活、便捷高效及成本低的独特优势。测试结果表明,水平井分段多簇细分切割体积压裂通过射孔限流+颗粒暂堵方式,能够实现100%多簇完全起裂,但各簇进砂(液)量差异明显,各簇裂缝延伸不均衡。该项研究初步回答了多簇起裂有效性问题,并验证了水平井套管内泵入式光纤监测技术的可行性,丰富了水平井体积压裂效果评估测试手段,同时为鄂尔多斯盆地页岩油水平井压裂工艺及参数优化提供了重要依据。

渤海C油田馆陶组储层堵塞实验评价研究

为了分析明确渤海C油田导管架期间预钻井的12口生产井,在组块安装后投产产量达不到配产目标的原因,针对有机质沉积、原油乳化堵塞、流体配伍性、钻完井液漏失与返排等潜在储层伤害因素,开展了储层堵塞实验评价研究。实验结果表明:1)免破胶无固相钻开液(EZFLOW)漏失量越高渗透率伤害程度越大,同时考虑钻完井液漏失时,天然岩心的渗透率伤害程度为37%,伤害程度中等;2)有机质沉积对储层伤害较为明显,注入0.4 PV原油后渗透率伤害程度达到98%,且随有机质沉积量的增加,储层伤害越大;3)油包水型乳状液(W/O型)驱替对岩心渗透率伤害程度高达75.01%,水包油型乳状液(O/W型)驱替对岩心渗透率伤害程度为25.21%,低含水层受原油乳化堵塞影响较明显。综合分析认为,渤海C油田12口预钻井低产原因为导管架预钻井后待组块安装期间关井静置过程中有机质沉积和原油乳化伤害。同时,渤海C油田12口预钻井目的层馆陶组储层物性因子较小,产液指数较低是导致低产的原因之一。研究结论为后续增产措施以及方案提供了依据。

油田监测用密度可控同位素示踪微球的制备及应用

制备了用于油田监测的同位素示踪微球,分析了微球的形貌、抗压强度、热性能、耐溶剂性和加工性能,揭示了微球与同位素产率及加工性能的构效关系,提出了示踪微球密度计算方法。结果表明:示踪微球表面形貌主要为致密和松散两种,抗压强度的影响因素主要为黏合剂种类与加料方式;采用不同黏合剂制备的微球耐溶剂性差别较大,采用酚醛胺和聚酰胺制备的示踪微球抗压强度较高,耐热性较好;采用炭粉为原料获得的同位素产率较高;微球密度的调控可以通过一个经验系数来计算。

基于AHP-熵权法的油田防垢技术优选研究

现阶段国内油田在不同生产环节防垢技术的选择上,缺少科学有效的评价体系。针对这一问题,经调研、对比、分析及筛选,明确了从安全性、适用性、技术难度、效能及经济性这五个纬度构建防垢技术水平判断指标,确定了防垢技术水平评价分为基础、标准、强化及综合防垢这四个等级,选择层次分析法(AHP)+熵权法(EWM)构建防垢技术选择的评价模型,对影响防垢技术选择的各项指标按照重要程度进行排序,对防垢水平进行评价,通过评价结果确定油田最终防垢方案,并根据具体防垢案例验证该方法的准确、可行及可靠性。通过构建防垢技术优选体系,能够有效判断不同防垢技术对目标油田的防垢水平,为油田防垢技术优选过程提供理论基础。

基于超音速膨胀凝结的油田伴生气脱二氧化碳研究

油田伴生气通常含有大量的二氧化碳等酸性气体,为了提升油田伴生气质量,必须对天然气进行脱二氧化碳处理;将超音速旋流分离技术用于伴生气脱除二氧化碳是一条全新路径,但二氧化碳在超音速流动条件下的冷凝特性有待进一步明晰。建立二氧化碳在喷管中的相变过程数学模型,讨论二氧化碳超音速凝结流动特性,分析入口温度和压力对二氧化碳超音速凝结特性的影响规律。结果表明:二氧化碳在喷管喉部之后的扩张段发生凝结,生成大量的二氧化碳液滴;随着喷管入口温度增加,尽管凝结的二氧化碳液滴数量增加,但喷管出口和中轴线上的液相质量分数减小,凝结位置越靠近喷管出口;随着喷管入口压力增加,混合气体在喷管出口的压力和温度升高、速度减小,二氧化碳在喷管内凝结产生的液滴数量减少,喷管出口和中心轴线上的液相质量分数越大。

长庆油田数智化油藏建设理论与实践

随着油气勘探认识和技术的不断进步,盆地边缘新层系非常规储层成为油气增储上产的重要领域,开采难度增加,工作量培增。然而,油田用工总量不增反降,如何提升油气藏研究的精细化水平,培育新质生产力,打造油田高质量发展新引擎,是油田急需解决的问题。长庆油田制定了“125”数智化油藏建设规划,通过数智化技术,助力资源勘探、油气开发和新能源3大主业的高质量发展。立足数智化油藏学科长远建设,结合地质研究、井位部署与随钻、产能建设、稳产提产等领域的数智化建设特点,总结出一套高效稳健的数智化油藏建设理论与方法,形成了“一体系四中台”基本建设思路,制定了勘探开发数智化整体解决方案。在该理论指导下,建成了数字油气藏研究与决策支持平台,有效推进了长庆油田的快速上产稳产,现已成为中国石油天然气集团有限公司的品牌产品,支撑着长庆油田向国际一流大油气田迈进。

准噶尔盆地永进油田侏罗系超深层致密砂岩储层成岩相识别及分布预测

深层致密砂岩储层非均质性强、分布规律复杂,地质甜点预测难度大。为实现高效勘探开发,如何准确识别与预测井间储层成岩相亟需深入研究。综合利用岩心、测井和三维地震资料,在准噶尔盆地永进油田侏罗系超深层储层成岩作用研究基础上,开展了成岩相识别及分布预测研究,认为储层成岩作用类型主要有压实作用、胶结作用及溶蚀与交代作用,可划分为强溶蚀+绿泥石包壳、中等溶蚀+自生高岭石、中等钙质胶结溶蚀、强钙质胶结及压实致密等5种成岩相。基于测井资料,利用岩石物理参数、物性参数对储层成岩相类型进行了综合识别,确定其垂向分布规律。研究发现强溶蚀+绿泥石包壳和中等溶蚀+自生高岭石这两种优势成岩相主要位于三角洲主干分流河道砂体内部,储层物性较好,是油层发育的主要部位。基于成岩相与地震纵波阻抗的对应关系分析,发现优势成岩相纵波阻抗相对较低,可通过纵波阻抗的数值分布特征预测优势成岩相分布。因此利用三维地震纵波阻抗反演成果开展了成岩相分布预测,根据纵波阻抗与不同类型成岩相对应关系落实了优势成岩相发育区。结果表明,优势成岩相主要位于研究区东北部的Y301—Y302井区以及西北部Y1井区,呈局部连片分布发育。储层成岩相识别可以为超深层地质甜点的分布预测研究提供重要依据。

大庆油田SEC储量折耗一体化评估模型

SEC储量是大庆油田有限责任公司经营决策的核心资产,是油气生产的物质基础。油气资产折耗和SEC储量相关,是完全成本中的重要构成部分,决定了油田经营效益。大庆油田进入双特高含水后期,开发对象变差导致增储能力变差、油气资产折耗上升,因此亟需开展SEC储量折耗一体化优化研究,使储量和折耗指标最优。结合折耗计算公式、ARPS递减模型和经济极限产量计算模型等公式,进行科学归纳和推导,建立了SEC储量折耗一体化增储模型,并且在量化分析各种影响因素的基础上,明确了储量和折耗的优化次序和参数,给油田开发经营提出建议。模型应用在大庆油田年度SEC储量评估中,使油田增储能力逐年提升,油气资产折耗得到有效控制。研究成果具有通用性和适应性,可以在国内其他油田推广应用。